In recent years, intake of high-fat foods in Japanese people has been increasing with the increasing westernization of their life style. The 1999 National Nutrition Survey reports that the fat energy ratio exceeds the proper level of 25% despite of the energy intake decreasing year by year and that 50 to 60 percent of the 60 and older population has high triglyceride levels or high cholesterol levels (Ministry of Health, Labor and Welfare of Japan. An overview of the results of the 1999 National Nutrition Survey. Japanese Journal of Clinical Nutrition 2001; 98(5): 577-588).
Obesity is one of the most important diseases in modern society, and mainly caused by excessive consumption of fats. Excessive consumption of fats is known to induce not only obesity but also obesity-associated conditions such as diabetes, hyperlipemia, hypertension and arteriosclerosis. An appetite suppressant Mazindol® is the only drug approved for this obesity in Japan, but it was reported to have adverse side effects such as dry mouth, constipation, stomach discomfort and nausea/vomiting (Clinical Evaluation 1985; 13(2): 419-459; Clinical Evaluation 1985; 13(2): 461-515). Outside Japan, a commercially available drug for improving obesity is Xenical®, which functions to suppress intestinal fat absorption by lipase inhibitory activity, but it is not always safe because it was also reported to have adverse side effects such as fatty stools, increased stool frequency, loose stools, diarrhea and abdominal pain (Lancet 1998; 352: 67-172).
An effective means to prevent obesity is to reduce caloric intake by dietary restrictions, but they should be supervised by an experienced nutrition counselor and it is often difficult to follow them in daily life. Thus, a safe and healthful way to inhibit the absorption of dietary fats by the body would be a practical and useful approach to the treatment of obesity and related diseases or health enhancement.
Against this background, attention has been given to the development of foods for specified health use with proven safety and effectiveness for humans. Foods for specified health use so far marketed as food materials for controlling the increase in serum triglyceride levels after eating include globin digests suppressing fat absorption by pancreatic lipase inhibition (J. Nutr. 1998; 128: 56-60; Journal of the Japanese Society of Nutrition and Food Science 1999; 52(2): 71-77; Journal of Health Food & Nutrition Food Studies 2002; 5(3): 131-144); diacylglycerols having different digestion/absorption characteristics from those of triacylglycerols (J. Am. Coll. Nutr. 2000; 19(6): 789-796; Clin. Chim. Acta. 2001; 11(2): 109-117); and eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) purified from fish oils, etc.
Attention is also recently being given to plant-derived materials having lipase inhibitory activity, and especially various polyphenols having lipase inhibitory activity have been reported, such as plant bark-derived tannin (Japanese Patent Publication Sho 60-11912); tannins and flavonoids and glycosides thereof contained in a legume Cassia nomame (Japanese Patent Laying Open Hei 8-259557); food products for inhibiting lipid absorption containing epigallocatechin gallate and epicatechin gallate known as major ingredients in green tea (Japanese Patent Laying Open Hei 3-228664); lipase inhibitors comprising aqueous extracts of green pepper, shimeji mushroom, pumpkin, maitake mushroom, hijiki seaweed, green tea, oolong tea, etc. (Japanese Patent Laying Open Hei 3-219872); flavones and flavonols (Japanese Patent Laying Open Hei 7-61927); hydroxybenzoic acids (gallic acid) (Japanese Patent Laying Open Hei 1-102022); triterpene compounds and derivatives thereof (Japanese Patent Laying Open Hei 9-40689); anti-obesity agents containing procyanidin from tamarind as an active ingredient (Japanese Patent Laying Open Hei 9-291039); as well as lipase inhibitory effects of grape seed extracts (Nutrition 2003; 19(10): 876-879); lipase inhibitory effects and anti-obesity effects in rats of Salacia-derived polyphenols (J. Nutr. 2002; 132: 1819-1824); and anti-obesity effects of oolong tea extracts in mice (Int. J. Obes. 1999; 23: 98-105).
However, plant-derived lipase inhibitors so far reported as shown above are not sufficiently effective. Even if an extract of a plant was effective, for example, it would be difficult to stably maintain lipase inhibitory activity unless the amount of the active ingredient contained in it is specified because it is naturally derived. Moreover, inhibitors derived from tasteless plants have the disadvantage that they affect flavor when they are used as foods or beverages. For example, there are several reports showing the effect of oolong tea in improving lipid profiles by demonstrating a significant decrease in blood triglyceride levels after drinking 1330 ml of commercially available oolong tea daily for 6 weeks (Journal of the Japanese Society of Nutrition and Food Science 1991; 44(4): 251-259) or a weight loss of 1 kg or more in 67% of subjects consisting of 102 men and women with simple obesity who continuously took oolong tea (2 g×4/day) orally for 6 weeks and a significant improving effect after ingestion of oolong tea in subjects showing high blood triglyceride levels (Journal of the Japanese Society of Clinical Nutrition 1998; 20(1): 83-90). Thus, beneficial effects have been observed by drinking plenty of oolong tea, but it is difficult to continue to do so in daily life. If simply concentrated oolong tea was provided, it would not be suitable as a practical means because of strong bitterness/astringency and high caffeine content.